yea so got a few ideas on the tyres, i really like the look of some black steels 17 inch seem to be the biggest, I have 18s on the Tekna. But is it worth buying a set of 4 steel sticking on the winter tyres and swoping them over. its actually easier to buy winter tyres for the 17inch steels as 215 5518 is such a hard size to source

Quesion is go for steels and winter tyres or just stick winters on tekna alloys?

buy a cheap set of steels and put the winters on those. It'll save you in the long run. Winter tyres are designed for temperature of 7 celcius and below. Though they do function fair well above that they will not last long or do the job as well as an all season / summer tyre.
If you are looking at a different wheel size i'd say don't. Having a larger or smaller wheel size than that fitted as standard will effect your vehicle in both its handling and speedo accuracy and maybe in other ways. With all the esp/ traction control / hill start / hill decent etc that the cars have these days who knows what problems it will cause.

For a few years I change wheels at my wife's car. I bought a set of alloy's (Which were CHEAPER than the same steel wheels!) and I gonna change them one of these days. I do it myself and the storage is no problem. The garage wanted 50 for each change and 50 a year for storage (!! Bandits...)
By the way: smaller (in width) tires give you more grip than wide(er) ones.... And during wintertime you drive not as fast as you normally do (at least I may hope so... )

in UK there ate TONS of 5x114.3 used wheels available. They are dirt cheap.

So i'd say go buy set of 16/17 inch wheels and mount winter tires on them. Much easier to swap them afterwards and youĺl save you 18 inchers